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Metal distribution, speciation, and bioavailability in stormwater management oil/grit chamber systems and marine receiving waters

University of British Columbia

The stormwater management practice of oil/grit chamber systems is utilized to reduce pollutants from urban/industrial runoff to natural waters. Metal determinations (Cu, Zn, Cd, Ni, Pb) were used to test chamber effectiveness, elucidate distribution patterns of total and labile (Cu, Cd, Ni only) metals in water and sediments, and examine influences on metal bioavailability. Water, sediment, and biota analyses revealed chambers do not function adequately in reducing dissolved, fine particulate-bound, colloidal, and DGT-labile metals. Runoff from industrial/commercial areas resulted in elevated bioavailabilities of Cu, Zn, Cd, and Pb. Cu and Zn were of significant concern, especially during the onset of the rainy season. Chamber systems appear to provide some reduction of metalbound coarse particles; however, significant portions of total metals easily flow into receiving water bodies. Furthermore, re-suspension of previously deposited particulate metals within chambers may provide additional opportunities for increased metal dissolution and lability. The diffusive gradient in thin film technique (DGT) used in water provided an indication of high metal discharge and proved to be a good measure of time-integrated average of elevated levels. Consequently, this technique can reflect effective metal means for whole storm event periods. DGT in water also effectively reflected bioavailabilities for the three elements assessed in the order (Cu>Cd»>Ni). For Ni , DGT may be more sensitive in discriminating between sites than bioaccumulations. Comparatively, the sediment DGT technique was not very effective due to large spatial and temporal variabilities; it is not recommended for environmental monitoring work, where these conditions may apply. The barnacle, Balanus glandula, was useful as a biomonitoring species and shows promise for future metal bioavailability work within its geographical range. Variability in metal bioaccumulations was noted as a result of substrata and vertical positioning and should be considered in any future studies using B. glandula as a metal biomonitor. Ideally, contaminant free substrata should be utilized for the prevention of potential influences from naturally occurring surfaces. Altogether, these studies indicate that oil/grit chambers function as poor primary treatments. Better stormwater detention capacity and metal removal processes are necessary to facilitate the goal of metal reduction in stormwater runoff to waterways.

Text

2009-12-23

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http://hdl.handle.net/2429/17088

Zoology

University of British Columbia

UBCV

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